Intramedullary fixation device and methods for bone fixation and stabilization

ABSTRACT

An internal intramedullary fixation device for the stabilization of bone in arthrodesis and fractures of the foot and hand is disclosed. During implantation in the medullary canal of each bone, the device grasps the edges of the canal, stabilizing the bone (internally) during the natural healing process.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/162,226, filed on Jan. 23, 2014, entitled“Intramedullary Fixation Device and Methods for Bone Fixation andStabilization”, which is a divisional application of U.S. patentapplication Ser. No. 13/084,048, filed on Apr. 11, 2011, entitled“Intramedullary Fixation Device and Methods for Bone Fixation andStabilization”, now U.S. Pat. No. 8,685,024 issued Apr. 1, 2014 andclaims the benefit of U.S. Provisional Application No. 61/324,080,entitled “The Arrowhead Fixation Device is an Intramedullary FixationDevice Used in Bone Fixation and Stabilization,” filed Apr. 14, 2010,each of which are incorporated herein by reference.

BACKGROUND

Hammertoe deformities occur when the metatarsophalangeal joint betweenphalanges in a toe are cocked upward and the proximal interphalangealjoint bends downward. This deformity can become quite painful and canlimit the ability of a person with hammertoe to walk and perform otherdaily activities. Hammertoe may be caused by any number of factors,including the long-term use of poorly fitting shoes, having a longsecond toe, hallux valgus pressing against the second toe, connectivetissue disorders and trauma.

While some minor cases may be treated with non-surgical remedies,surgeries are often necessary to provide real correction and painrelief. Some surgical methods include stabilizing the toes using asmooth K-wire placed in an antegrade manner through the middle anddistal phalanges while joint extension and distraction are maintained.The K-wire may then be placed in retrograde fashion into the proximalphalanx while joint extension and distraction are maintained. Fixationlasts for 4-6 weeks after surgery. During that time, the pins are cappedso that the sharp ends do not catch on objects, such as bed sheets. Evenwith this form of fixation, non-unions, K-wire migration, and loss offixation can be quite common. Further, the external K-wires may lead topin tract infections or movement of bone along the smooth wire,including rotation of the distal aspect of the toe. These types ofchallenges make alternative fixation methods desirable.

The devices and methods disclosed herein overcome one or more of theproblems in the prior art.

SUMMARY

In one exemplary aspect, the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilization.The device may include an arrowhead-shaped distal head comprising adistal end having a sharp point and comprising first, second, third, andfourth outwardly facing side surfaces forming a pyramidal shape. Thefirst and third side surfaces may be opposed from each other and mayform a first angle, and the second and fourth side surfaces may beopposed from each other and may form a second angle. The second anglemay be different than the first angle. Each of the first and third sidesurfaces may have a proximally projecting edge forming a tip of a barb.The barbs may be configured to engage tissue and inhibit rotationalmovement and inhibit axial movement of the distal head in a proximaldirection. The device may also include an arrowhead-shaped proximal headcomprising a proximal end having a sharp point and comprising fifth,sixth, seventh, and eighth outwardly facing side surfaces. The fifth andseventh side surfaces may be opposed from each other and may form athird angle. The sixth and eighth side surfaces may be opposed from eachother and may form a fourth angle, with the third angle being differentthan the fourth angle. Each of the fifth and seventh side surfaces mayhave a distally projecting edge forming a tip of a barb. The barbs maybe configured to engage tissue and inhibit rotational movement andinhibit axial movement of the proximal head in a distal direction. Arigid body extends between and connects the distal head and the proximalhead. The body may have a rigidity sufficient to withstand bendingloading applied by the phalanges.

In another exemplary aspect, the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilization.The device may include an arrowhead-shaped distal head having first,second, third, and fourth outwardly facing side surfaces forming apyramidal shape. The first and third side surfaces may be opposed fromeach other and may form a first angle, and the second and fourth sidesurfaces may be opposed from each other and may form a second angle.Each of the first and third side surfaces may have a proximallyprojecting edge forming a tip of a barb. The barbs being configured toengage tissue and inhibit movement of the distal head in a proximaldirection. The second and fourth side surfaces lack proximal edgesforming barbs. The device may also include an arrowhead-shaped proximalhead having fifth, sixth, seventh, and eighth outwardly facing sidesurfaces. The fifth and seventh side surfaces may be opposed from eachother and may form a third angle, and the sixth and eighth side surfacesmay be opposed from each other and may form a fourth angle. Each of thefifth and seventh side surfaces may have a distally projecting edgeforming a tip of a barb. The barbs may be configured to engage tissueand inhibit movement of the proximal head in a distal direction. Thesixth and eighth side surfaces may lack proximal edges forming barbs.The device also may include a cylindrical body extending between andconnecting the distal head and the proximal head. The cylindrical bodymay have a rigidity sufficient to withstand bending loading applied bythe phalanges.

In another exemplary aspect, the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilization.The device may include an arrowhead-shaped distal head comprising adistal end having a sharp point and comprising first, second, third, andfourth outwardly facing side surfaces forming a pyramidal shape. Thefirst and third side surfaces may be opposed from each other and mayform a first angle, and the second and fourth side surfaces may beopposed from each other and may form a second angle, with the secondangle being different than the first angle. Each of the first and thirdside surfaces may have a proximally projecting edge forming a tip of abarb. The distal head also may include a first undercut and a secondundercut, where each of the first and second undercuts have a depth suchthat the barb tips are disposed proximal of the respective undercut. Thebarbs may be configured to engage tissue and inhibit movement of thedistal head in a proximal direction. The derive may also include anarrowhead-shaped proximal head comprising a proximal end having a sharppoint and comprising fifth, sixth, seventh, and eighth outwardly facingside surfaces. The fifth and seventh side surfaces may be opposed fromeach other and may form a third angle, and the sixth and eighth sidesurfaces may be opposed from each other and may form a fourth angle,with the third angle being different than the fourth angle. Each of thefifth and seventh side surfaces may have a distally projecting edgeforming a tip of a barb. The proximal head also may comprise a thirdundercut and a fourth undercut. Each of the third and fourth undercutsmay have a depth such that the barb tips are disposed distal of therespective undercut. The barbs may be configured to engage tissue andinhibit movement of the proximal head in a distal direction. A rigidbody extends between and connects the distal head and the proximal head.The body may have a rigidity sufficient to withstand bending loadingapplied by the phalanges. It may comprise a main portion, a distal neckportion, and a proximal neck portion. The distal and proximal neckportions may have a cross-sectional area smaller than a cross-sectionarea of the main portion. The distal neck portion may support the distalhead and the proximal neck portion may support the proximal head. Thedistal neck may intersect with the first and second undercuts in thedistal head and the proximal neck may intersect with the third andfourth undercuts in the proximal head.

In yet another exemplary aspect, the present disclosure is directed to akit for bone fixation and stabilization. The kit may comprise anintramedullary fixation device and insertion forceps. The intramedullaryfixation device may comprise an arrowhead-shaped distal head havingfirst, second, third, and fourth outwardly facing side surfaces forminga pyramidal shape. The first and third side surfaces may be opposed fromeach other and may form a first angle, and the second and fourth sidesurfaces may be opposed from each other and may form a second angle.Each of the first and third side surfaces may have a proximallyprojecting edge forming a tip of a barb. The barbs may be configured toengage tissue and inhibit movement of the distal head in a proximaldirection, and wherein the second and fourth side surfaces lack barbs.The device may also comprise an arrowhead-shaped proximal head havingfifth, sixth, seventh, and eighth outwardly facing side surfaces. Thefifth and seventh side surfaces may be opposed from each other and mayform a third angle, and the sixth and eighth side surfaces may beopposed from each other and may form a fourth angle. Each of the fifthand seventh side surfaces may have a distally projecting edge forming atip of a barb. The barbs may be configured to engage tissue and inhibitmovement of the proximal head in a distal direction. The sixth andeighth side surfaces may lack barbs. A cylindrical body extends betweenand connects the distal head and the proximal head. The cylindrical bodymay have a rigidity sufficient to withstand bending loading applied bythe phalanges. The insertion forceps may be configured to securablygrasp the intramedullary fixation device, and may include a first nosepiece having a first recess formed therein. The first recess may besized to receive a portion of the cylindrical body of the intramedullaryfixation device. The insertion forceps may also include a second nosepiece having a second recess formed therein. The second recess may besized to receive a portion of the cylindrical body of the intramedullaryfixation device. The first and second nose pieces may be cooperativelyarranged to securely grip the cylindrical body of the intramedullaryfixation device sufficiently to prevent rotation and axial displacementunder normal insertion conditions.

In yet another exemplary aspect, the present disclosure is directed to amethod comprising a step of grasping an intramedullary fixation device,introducing a proximal end of the device into an intramedullary canal ofa first bone element, introducing a distal end of the device into anintramedullary canal of a second bone element, releasing theintramedullary fixation device, and pressing the first and second boneelements together.

In yet another exemplary aspect the present disclosure is directed to anintramedullary fixation device used in bone fixation and stabilization.The device comprises an arrowhead-shaped distal head comprising a distalend having a sharp distal point and also comprising distal first,second, and third outwardly facing side surfaces converging toward andintersecting at the distal point. The distal first outwardly facingsurface may have a maximum width greater than a maximum width of thedistal second outwardly facing surface. At least one of the distalfirst, second, and third outwardly facing surfaces may have a proximallyprojecting edge forming a tip of a barb configured to engage tissue andinhibit rotational movement and inhibit axial movement of the distalhead in a proximal direction. The device also comprises anarrowhead-shaped proximal head comprising a proximal end having a sharpproximal point and also comprising proximal first, second, and thirdoutwardly facing side surfaces converging toward and intersecting at theproximal point. The proximal first outwardly facing surface may have amaximum width greater than a maximum width of the proximal secondoutwardly facing surface. At least one of the proximal first, second,and third outwardly facing surfaces may have a distally projecting edgeforming a tip of a barb configured to engage tissue and inhibitrotational movement and inhibit axial movement of the proximal head in adistal direction. A rigid body extends between and connects the distalhead and the proximal head. The body may have a rigidity sufficient towithstand bending loading applied by the phalanges. In yet additionalembodiments, the present disclosure is directed to a kit including theintramedullary fixation device. In yet additional embodiments, thepresent disclosure is directed to methods for implanting theintramedullary fixation device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary intramedullary fixation devicedisposed between and within adjacent phalanges of a toe of a patient inaccordance with one aspect of the present disclosure.

FIG. 2 is an illustration of the exemplary intramedullary fixationdevice of FIG. 1 in accordance with one aspect of the presentdisclosure.

FIG. 3 is an illustration of a side view of the exemplary intramedullaryfixation device of FIG. 2 in accordance with one aspect of the presentdisclosure.

FIG. 3A is an illustration of a cross-sectional view along lines 3A inFIG. 3 through a head of the intramedullary fixation device of FIG. 3.

FIG. 4 is an illustration of another side view of the exemplaryintramedullary fixation device of FIG. 2 rotated 90 degrees from theside view of FIG. 3.

FIG. 4A is an illustration of a cross-sectional view along lines 4A inFIG. 4 through a head of the intramedullary fixation device of FIG. 4.

FIG. 5 is an illustration of another exemplary intramedullary fixationdevice in accordance with one aspect of the present disclosure.

FIG. 6 is an illustration of another exemplary intramedullary fixationdevice in accordance with one aspect of the present disclosure.

FIGS. 7 and 7A are illustrations of an exemplary reamer surgicalinstrument usable for implantation of an intramedullary fixation devicein accordance with one aspect of the present disclosure.

FIGS. 8 and 8A are illustrations of an exemplary broach surgicalinstrument usable for implantation of an intramedullary fixation devicein accordance with one aspect of the present disclosure.

FIGS. 9 and 9A are illustrations of an exemplary insertion tool surgicalinstrument usable for implantation of an intramedullary fixation devicein accordance with one aspect of the present disclosure.

FIG. 10 is a flow chart of an exemplary surgical method of implanting anintramedullary fixation device in accordance with one aspect of thepresent disclosure.

FIG. 11 is an illustration of an exemplary intramedullary fixationdevice disposed between and within adjacent phalanges of a finger of apatient in accordance with one aspect of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of various embodiments.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. In addition, the present disclosuremay repeat reference numerals and/or letters in the various examples.This repetition is for the purpose of simplicity and clarity and doesnot in itself dictate a relationship between the various embodimentsand/or configurations discussed.

The present invention relates to an intramedullary fixation device usedfor bone fixation and stabilization of toes and fingers across fusion orfracture sites, and treat deformities, including for example, hammertoedeformities. The intramedullary fixation device includes a unique arrowdesign on both its proximal and distal ends. It is arranged to becompletely intramedullary when implanted with no parts of the deviceexposed outside the skin. Further, it is arranged to resist therotational and pull-out forces affecting the lesser toes. Its particulardesign shape may help it maintain the initial compression applied atinsertion.

In addition, because of its convenient dual locking design, theintramedullary fixation device enables health care providers to performimplantation procedures faster and with less effort than priortechniques, such as those using external wires, such as K-wires. Forexample, it may require little or no bone removal when preparing fordevice insertion, potentially decreasing trauma and reducing recoverytimes. Further, the intramedullary fixation devices disclosed herein mayremain permanently implanted. Accordingly, there is no need to schedulean additional procedure to remove this device as is necessary withtemporary fixation devices, such as is required with K-wire fixation. Assuch, the intramedullary fixation devices disclosed herein may provide amore comfortable recovery, a lower incidence of infections, and theavoidance of that additional and often very uncomfortable procedure toremove the K-wire implant. Further, unlike the K-wire implants, thearrow designs at each end of the implant lock into bone reducing osseousmovement or rotation.

FIG. 1 shows an exemplary toe 10 having an intermediate phalanx 12 and aproximal phalanx 14. In this example, the toe 10 has been surgicallytreated to correct a deformity such as hammertoe as discussed above.Accordingly, the toe includes an implanted intramedullary fixationdevice 100 disposed therein in accordance with an exemplary aspect ofthe present disclosure. In this example, the device 100 extends betweenand is implanted within the intermediate and proximal phalanges 12, 14.It is described in detail below.

FIGS. 2-4 show one exemplary embodiment of the device 100 of the presentapplication. The device 100 is designed with a three-dimensionallyconfigured arrow at each end and includes a first head 102, a secondhead 104, and a body 106 extending between the first and second heads102, 104. As will become apparent from the below description, theindividual components of the device 100 work in conjunction with oneanother to stabilize bone during arthrodesis procedures and acrossfractures. For reference, this disclosure refers to the first head 102as a distal head and the second head 104 as the proximal head.

The distal head 102 is formed as a three dimensional arrowhead that issized for placement in an intramedullary canal of a patient. It isconfigured so that edges of the arrowhead grasp the bone in themedullary canal as it is inserted, stabilizing the arthrodesis or fusionsite during the osseous union. In this exemplary embodiment, the distalhead 102 is formed as a distal end having a distal-most point 108. Thedistal-most point 108 leads the device 100 down the reamed or broachedinsertion channel to its final implantation site during insertion. Inthis example, the distal-most point 108 is a sharp point arranged toglide through tissue within the intramedullary canal to ease insertion.The sharp point 108 also may reduce trauma occurring due to a ripping ortearing effect that may occur with blunt or rounded tips. Otherconfigurations of the arrowhead's tip may result in successful insertionbased on preparation of the insertion site.

First, second, third, and fourth outer facing surfaces 110, 112, 114,116 intersect at and extend from the distal most point 108 in theproximal direction, forming a four-sided pyramidal shape. Although shownas having four outer facing surfaces, some embodiments include greateror fewer outer facing side surfaces. In the example shown, opposingsurfaces angle away from each other to define a leading angle. Forexample, the opposing first and third outer facing surfaces 110, 114define an angle θ of the arrowhead shaped distal head 102. In someexamples, the angle θ is in the range of about 30 degrees to about 90degrees. In other examples, the angle θ is in the range of about 50 to70 degrees, and in some embodiments, the angle is around 60 degrees. Ina similar manner, the opposing second and fourth outer facing surfaces112, 116 of the arrowhead shaped distal head 102 form an angle α. In theexample shown, the angle α is smaller than the angle θ. The angle α maybe selected to be within the range of about 10-40 degrees, and in someembodiments, is in the range of about 15-25 degrees. In some examples,the angle α is about 19 degrees. The multiple angles described on thedistal head may vary based on the size and strength of bone in which thedevice is to be implanted.

Because of the different angles between the opposing first and thirdsurfaces 110, 114 and the opposing second and fourth surfaces 112, 116,the width of the distal head 102 differs from side to side. This is bestseen in FIG. 3A, showing a cross-sectional view of the distal head 102taken through the section 3A in FIG. 3. For example, FIG. 3A shows awidth w1 of the first and third outer facing surfaces 110, 114 beingless than a width w2 of the outer facing surfaces 112, 116. Thisdiffering width increases resistance to rotation that may occur if thedevice 100 were cylindrical or to a lesser extent substantially square,although such embodiments are contemplated. Further, the differing widthmay permit an implanted device to be removed, rotated 90 degrees andimplanted again while still providing satisfactory anchoring.

Returning to FIG. 3, the distal head 102 may be sized to have atransverse width w3 greater than a longitudinal length L. The transversewidth w3 may be sized in the range 2-6 mm and the longitudinal length Lmay be sized in the range of about 1.5-5.5 mm. In one example, thetransverse width w3 is around 3.5 mm and the longitudinal length L isabout 3 mm. Other sizes however, both larger and smaller, arecontemplated, and in one example, the width and the length aresubstantially equal.

In the example shown, the distal head 102 includes two proximallyprojecting barbs 118, 120. These barbs are configured to engage tissuewithin the intramedullary canal and resist movement and migration and/oraxial displacement within the canal once they have been inserted intothe canal. As can be seen, these barbs 118, 120 are formed by edges ofrespective outer facing surfaces 110, 114 and because of the pyramidalshape of the distal head, the edges lie in substantially parallel lines.

Inner surfaces of the barbs 118, 120 are formed by first and secondundercuts 122, 124 disposed respectively between tips of the barbs 118,120 and the body 106. In this example, the undercuts are formed so thatthey cut into the body in a direction and at a location distal ofproximal tips of the barbs 118, 120. This is shown also in thecross-sectional view of FIG. 4A, taken along lines 4A in FIG. 4. In thisexample, the undercuts 122, 124 are formed by arcing surfaces. Becauseof the curvature, the arcing surfaces have a distal peak that is distalof the tips of the barbs 118, 120 themselves. The undercut surfaces 122,124 merge with the body 106 to provide greater pull-out resistance. Theshape shown, with its arcing surfaces, may expose a larger surface areato cancellous bone, thereby increasing the resistance to the pull-outforces as compared to a straight surface. The undercuts themselvesprovides space that accommodates bony ingrowth to provide additionalpull-out resistance and further stabilize the implant during healing andfusion. While in the example shown, the barbs are substantially rigid orinflexible, in other embodiments, the undercut may also serve to allowthe barbs to flex when the implant becomes lodged in hard cortical bone.In some embodiments, the undercuts are formed with surface profiles orshapes other than proximal arcs. For example, some embodiments haveundercuts that are formed with substantially flat surfaces disposeddistal of tips of the barbs 118, 120. These may be transverse to thelongitudinal direction of the device 100. Other embodiments haveundercuts that project deeply into the distal head 102, substantiallyparallel to the angled outer facing surfaces 110, 114. These may besuitable when less pull-out strength is needed. Because there is onlyone barb 118, 120 along each side of the device 100, insertion mayresult in less tissue disruption than an arrow having multiple barbs orhaving a several points of equal maximum width. As a result of lowertrauma, the tissue itself may be more intact for securing the barbs andresisting removal or axial displacement from the intramedullary canal.

The body 106 extends between and connects the distal head 102 and theproximal head 104. It is a one-piece rigid element structurallyconfigured to withstand loading applied across the joint or fracturebeing supported. It includes a main body portion 130 and necks 132, 134at either end leading to the distal and proximal heads 102, 104. As canbe seen, the main body portion 130 has a diameter larger than that ofthe necks 132, 134. For the reasons explained below, the larger bodyportion 130 may be easier to grasp and secure because it has a largerperimeter surface area, while the necks 132, 134 may be sized to permitadditional tissue placement and tissue growth immediately adjacent theundercut surfaces 122, 124 of the distal and proximal heads 102, 104.This may result in more secure and lasting anchoring. Thus, thisstructural arrangement may provide space for extra tissue to grow behindthe arrowhead to aid in fixation, while still providing a large grippingsurface on the body 106. In the embodiment shown, the diameter of themain body 130 is in the range of about 1-3 mm, and preferably has adiameter around 1.5 mm. Both larger and smaller diameters arecontemplated. In the example shown, the main body 130 is cylindricallyshaped, which provides consistent strength characteristics through thelength of the implant. Further, the diameter is substantially consistentalong its length in order to permit the implant to be gripped withinsertion tools at any point along the main body in order to best fitthe anatomic variations of the phalanges. Because the main body has around profile, the body may be gripped with an insertion tool at anydesired rotational orientation relative to the tool, permitting thehealth care provider to orient and penetrate the desired bone location.The length of the body 106 is selected so that the opposing distal andproximal heads lie at the desired location within the phalanx wheninserted in the bone. Accordingly, without limitation, in someembodiments, the length of the device 100 is within a range of about10-50 mm, and the body 106 has a length of 7-44 mm. In one example, thelength of the body 106 is in the range of about 7-15 mm, and in oneexample, has a length of about 13 mm. Both larger and smaller bodies arecontemplated.

Still referring to these figures, the second and fourth outer facingsurfaces 112, 116 are angled and intersect with the body 106 at the neck132. In some examples, the second and fourth outer facing surfaces 112,114 may smoothly transition to the neck and in other examples, thesecond and fourth outer facing surfaces 112, 114 meet the neck 132 at anintersecting angle. In some examples, the neck 132 is formed with arounded perimeter having a diameter substantially similar to thedistance between the proximal ends of the second and fourth outer facingsurfaces 112, 114.

In the exemplary embodiment shown, each of the edges joining adjacentouter facing surfaces 110, 112, 114, 116 is chamfered or rounded,resulting in less sharp edges. This may be best seen in thecross-sectional view shown in FIG. 3A. In the example shown, the distalhead 102 includes chamfers 136 formed at 45 degree angles relative tothe outer facing surfaces 110, 112, 114, and 116. Other embodimentshowever, include chamfers at other angles or rounds with a radius thatprovides smooth transition from one outer facing surface to another. Assuch, in some examples, tissue may be more likely to be deflected andpushed aside during advancement of the distal head into the tissue thanto be cut by what might otherwise be sharp 90 degree edges betweenadjacent outer facing surfaces 110, 112, 114, 116. This may result inbetter purchase because tissue may be better left intact duringinsertion of the device 100.

The second or proximal head 104 is, in the example shown, substantiallysimilar to the distal head 102, but extends from the body 106 in theopposing direction. For clarity and to reduce duplication, thedescription above of the proximal head is not repeated here with theunderstanding that the description above applies equally to the proximalhead 104. The distal and proximal heads, due to their shape and opposingconfiguration, resist migration, pullout, and rotation.

The proximal and distal heads 102, 104 and the body 106 are, in theexample shown, equivalent to one another having substantially the samesize and configuration. In some examples however, the size orconfiguration of the distal and proximal heads are different. Forexample, the angle α between the second and fourth outer facing surfaceson the proximal head may be larger or smaller than the angle between thesecond and fourth outer facing surfaces on the distal head. Likewise,the angle θ between the first and third outer facing surfaces on theproximal head may be larger or smaller than the angle between the secondand fourth outer facing surfaces on the distal head. In some examples,the distal and proximal heads are merely scaled in size relative to eachother. In one example, the transverse widths w₃ of the distal head andthe proximal head are substantially equally sized at about 3.5 mm andthe longitudinal lengths L are equally sized at about 3.0 mm. In anotherexample, the transverse width w₃ of the proximal head is about 3.5 mm,and the transverse width of the distal head is selected as one of about2.0 mm, about 2.5 mm, and about 3.0 mm. In another example, thetransverse width of the proximal head is selected to be about 4.0 mm,and the transverse width of the distal head is selected to be about oneof about 2.0 mm, about 3.0 mm, and about 3.5 mm. The size of the distaland proximal heads may be selected based on their intended utility,including whether the device is intended for implantation in a toephalanx or a finger phalanx or across a fracture, for example. Becausenot all medullary canals have the same diameter, a health care providermay select an implant to achieve a desired fit. For example, a healthcare provider may accommodate situations where the proximal phalanx hasa larger medullary canal than the medullary canal of the intermediatephalanx. Although described as though the proximal head is larger thanthe distal head, in some examples the distal head may be sized largerthan the proximal head by any of the dimensions discussed above.Although particular maximum widths are provided as examples here, thesizes may be dimensioned larger or smaller than those indicated, andsizes may be offered in any desired size increment. Further, the anglesmay differ based on the size or diameter of bones to be treated.Accordingly, the device 100 may be sized to fit a wide range ofanatomies, as well as different joints of the phalanges.

The device 100 may be sterilized and may be formed of biocompatiblematerials, including stainless steels and titanium as well asnon-metallic materials, such as composites, polymers, andbioresorbables. In one example the device is formed of 316L (F138)stainless steel. In some examples, the device 100 is manufactured from asolid bar by a mechanical metal removal process, such as machining.After machining, the product may be passivated per ASTM A967-96 toremove any surface contaminants. It may then be electro-polished toimprove the surface finish and edge finish and may be laser marked foridentification. Some designs may lend themselves to a metal injectionmolding process.

FIG. 5 shows another embodiment of the device 100. For reference thedevice in FIG. 5 will be referenced by the numeral 100 a. Since many ofthe features are the same as the device 100 in FIGS. 2-4, only thedifferences will be described in detail. The device 100 a includes abody 106 a formed of a main body portion 130 a having a plantar gradebend 200. In this example, the bend 200 is a 10 degree plantar gradebend. Different embodiments include a bend that may be selected in therange of about 5-25 degrees. In some examples, the bend is selected tobe about a 15 degree bend, while yet other embodiments the bend isselected to be about a 5 degree bend. The bend divides the body portion130 a into a first portion 202 and a second portion 204. The first andsecond portions 202, 204 respectively define first and secondlongitudinal axes that intersect at the bend 200. In some examples, thebend 200 is disposed at a location within a range of about 40-80% of thelength of the body portion 130 a. In some examples, the bend is within arange of about 50-70% of the length of the body portion 130 a. In someexamples, the bend is at about 60% of the length of the body portion 130a. In other examples however, the bend 200 is disposed at otherlocations. Although shown with a 10 degree bend, other embodimentsinclude a bend angled within a range of about 5-30 degrees, and in someexamples, angled within a range of about 7-15 degrees. In some examples,the longer segment is particularly suited for accommodating the proximalphalanx and the shorter segment is particularly suited for accommodatingthe intermediate segment. Like the embodiments described above, thedevice 100 a is formed of a single solid, monolith material.Accordingly, there are no seams, welds, joints, or other stressintroducers. Whether to use a straight or bent configuration will dependon the deformity. The bent device 100 a provides a similar bend to thebone structure at the fusion/fracture site.

FIG. 6 shows another embodiment of the device 100. For reference thedevice in FIG. 6 will be referenced by the numeral 100 b. Since many ofthe features are the same as the device 100 in FIGS. 2-4, onlydifferences will be described in detail with the understanding thatother details and much of the description above applies equally to thedevice 100 b. The device 100 b includes first and second heads 102 b,104 b. Like the heads described with reference to FIGS. 2-4, the firstand second heads 102, 104 are three dimensional arrowheads.

For convenience, only the first head 102 b, referred to as the distalhead, will be described in detail. The distal head 102 b includes asharp distal-most point 108 b. First, second, third, and fourth outerfacing surfaces extend from the distal most point 108 b in the proximaldirection, forming a pyramidal shape. In FIG. 6, only two outer facingsurfaces 110 b, 112 b of the four outer facing surfaces are shown. It isunderstood that the opposing, non-visible surfaces are substantiallyidentical to the surfaces 110 b, 112 b shown. In this embodimenthowever, the outer facing surface 110 b and its opposing surface are notentirely planar, but are shaped slightly convex with a large radius suchthat the outer facing surface 110 b arcs between the adjacentsubstantially planar side surface 112 b and the outer facing surfaceopposing surface 112 b. Because of this, the barbs 118 b, 120 c alsoinclude a slightly arched or rounded shape. Here, the radius of the arcis sized larger than a width of or diameter of the implant itself.

Intersections of adjacent outer facing surfaces form edges that, in thisexample, are not chamfered or rounded. However, because of the slightlyconvex surface shape of at least two of the outer facing surfaces, theedges in this example still do not form true right angles, but formangles less than 90 degrees. It should be noted that 90 degree anglesare also contemplated.

FIGS. 7-9 show surgical instruments that may be used to implant thedevices described above. FIGS. 7 and 7A show a reamer 300, FIGS. 8 and8A show a broach 320, and FIGS. 9 and 9A show insertion forceps 340.

Turning first to FIG. 7, the reamer 300 may be formed of a length ofstainless steel wire having a diameter selected to penetrate and fitwithin and create pilot holes in intramedullary canals of toe or fingerphalanges without removing bone. In one embodiment, the reamer 300 mayhave a diameter of about 1.6 mm. The reamer 300 may include a smoothtrocar tip 302 configured to create a pilot hole without removing bone.In some examples, the reamer 300 includes markings 304 that serve as adepth gauge when reaming intramedullary canals. FIG. 7A shows the tip302 in greater detail with laser markings 304 spaced, for example, atincrements of 5 mm. Other embodiments include markings at differentintervals, while yet other embodiments include a single markingindicating a pre-established depth. Some embodiments do not include anymarkings at all and the surgeon estimates the depth of the reamer 300.

FIG. 8 shows the broach 320 in greater detail. The broach is sized andconfigured for insertion into the pilot holes created by the reamer 300to prepare the pilot hole for insertion of the device 100. Here, thebroach 320 includes a handle 322 and a broach tool 324. In someexamples, the diameter of the broach tool 324 is double the diameter ofthe reamer 300. The broach tool diameter may be, for example, selectedto be within a range of about 1.5-5.0 mm. In other examples, thediameter is selected to be within a range of about 2.5-3.5 mm. In someexamples, the broach tool 324 is sized with a diameter of about 3.2 mm.Diameters larger and smaller are contemplated. In the example shown, thebroach tool 324 includes a pointed conical tip 326 having an angle thatmatches the greatest angle of the distal and proximal heads 102, 104 ofthe device 100. For example, if the device 100 includes first and thirdoutwardly facing surfaces 110, 114 forming an angle θ of, for example,60 degrees, then the angle formed by sides of the conical tip 326 of thebroach tool 324 may also be angled at 60 degrees. In other examples, thetip angle may be vary from the greatest angle of the distal and proximalheads, and may, for example, be selected to match the angle α formed bythe second and fourth outer facing surfaces 112, 116. In otherembodiments, the tip angle is larger or smaller than the angles of theouter facings surfaces.

FIG. 8A shows a part of the broach tool 324 in greater detail. In someexamples, the broach tool 324 includes markings 328 that serve as adepth gauge when enlarging the pilot hole in the intramedullary canals.In this example, the laser markings 328 are spaced, for example, atincrements of 5 mm. Other embodiments include markings at differentintervals, while yet other embodiments include a single markingindicating a pre-established depth. Some embodiments do not include anymarkings at all and the surgeon estimates the depth of the broach tool324. In the example shown, the broach tool 324 includes a sharp pointand blade edges in order to penetrate the hard subcondral bone lyingjust beneath the cartilagenous surfaces. In a similar way, the sharppoint and blades facilitate penetration of hard sclerotic bone. Thebroach shaft profile then rapidly increases in diameter to a profilemore closely approximating that of the three dimensional arrow in orderto facilitate the insertion of the definitive implant. The broach widthis sized in relation to the implant to provide the proper balancebetween ease of insertion and resistance to rotational and pull-outforces. In some examples, this value ranges between 70% and 85% of theimplant width and in one embodiment is about 77% of the implant width.

FIG. 9 shows the insertion forceps 340 in greater detail. The insertionforceps 340 have a grasping end 342 formed of first and second nosepieces 344, 346 pivotably connected in a manner to close upon and gripthe device 100 and have a gripping end 348 with a locking mechanism 350that secures the forceps 310 in a clamping position. As shown in FIG.9A, each nose piece 344, 346 includes a transverse semicircular recess352, 354 formed therein, aligned with each other when the nose pieces344, 346 are adjacent each other. The recesses 352, 354 are formed in amanner permitting frictional engagement about the body 106 of the device100 to secure it against both rotational and axial displacement relativeto the insertion forceps 340. In the example shown, the recesses areround to match the cylindrical shape of the body 106 of the device 100.Because of the cylindrical shape of the body 106, the insertion forceps340 can be oriented a full 360° in relation to the arrowhead tip toaccommodate surgeon preference or anatomical variations. The radiusdimension is determined based on the diameter of the body 106 in orderto properly mate with the body 106. In some examples, the diameterformed by the two opposing recesses is within a range of about 5-15%smaller than the diameter of the body 106, thereby ensuring a securegrip on the device 100. In one example, the diameter of the body 106 isabout 1.50 mm, then the recesses 352, 354 may each have a radius of 0.70mm, together forming a diameter of 1.4 mm. In other examples, the radiusis sized to substantially match that of the body 106. Both larger andsmaller recesses are contemplated. It is to be noted that the larger thediameter of the body 106, the greater the surface area that is incontact with the insertion forceps, increasing frictional resistance.Therefore, a relatively large diameter of the body 106 may be desirable,resulting in a matching relatively large diameter of the recesses 352,354. During use, the insertion forceps 340 can be used to create apositive stop that prevents the implant from inadvertently beinginserted to a greater depth than desired. In addition, it can create avisual representation of the depth to which the surgeon desires to placethe implant. Further, it is configured in a manner providing a safesurface upon which to strike should the implant need additional force toprogress down the reamed intramedullary canal.

In some examples, the device 100 is provided as a kit with one or moreof the instruments described above. One exemplary kit includes a device100 as described above, with the reamer 300, the broach 320, and theinsertion forceps 340. Another exemplary kit includes both the device100 and the device 100 a, along with the reamer 300, the broach 320, andthe insertion forceps 340. Other exemplary kits include only one of theinstruments with one or more of the devices 100, 100 a. In one example,the kit includes a sterilized device 100, 100 a and sterilized, singleuse instruments including one or more of the reamer 300, the broach 320,and the insertion forceps 340. In another example, the kit includes asterilized device 100, 100 a, and multiple use instruments including oneor more of the reamer 300, the broach 320, and the insertion forceps340. Some kit embodiments include a plurality of devices 100, 100 a,with the instruments. In one example, a kit includes six devices and oneset of instruments. In one example, the instruments are provided in anautoclavable tray (not shown) for sterilization. Other kits andarrangements are also contemplated.

FIG. 10 is a flow chart describing an exemplary surgical method 400 forimplanting the device 100 using the instruments disclosed herein. Asbecomes apparent from the description below, the arrowhead configurationof both the distal and proximal heads 102, 104 captures bone on bothsides of the fusion or fracture site, and may provide internalstability. This is accomplished by pressing and locking the distal andproximal heads 102, 104 into the surrounding bone. The body 106 of thedevice 100 extends from each head (proximal and distal) and is theportion of the implant that crosses or spans the fusion or fracturesite.

The method begins at a step 402 where a health care provider estimatesthe diameter and length of the implant based upon pre-operativeplanning. In some examples, this is accomplished by taking and examiningpre-op radiographs to estimate the inner diameter of the intramedullarycanals of the affected phalanges at the location where the distal andproximal heads of the device 100 are expected to engage. In one example,this includes measuring with a ruler the inner diameter at the point ofengagement in the bone. In some examples, the health care providercalculates the diameter by overlaying an image of the implant upon thepatient's radiograph taking into account radiograph magnification. Thedevice may be selected so that the inner diameter of the intramedullarycanal is at least the same width as the distal or proximal head.Accordingly, in some examples, to achieve an effective fit, the healthcare provider selects a device with different sized heads. This mayincrease the likelihood of achieving proper purchase, may easeinsertion, and may mitigate impingement of the arrow barbs upon thecortices. The step of selecting the implant based on size may alsoinclude estimating the proper length of the device 100 that will engageeach phalanx at the desired point of contact. This projected length willalso enable the health care provider to approximate the broaching depthfor each phalanx.

At a step 404, the health care provider exposes the head of the proximalphalanx and the proximal end of the intermediate phalanx. This may beaccomplished by creating an incision over the point of implantation anddissecting through the skin and subcutaneous tissues to expose the headof the proximal phalanx. Tissue may then be removed from the proximalend of the intermediate phalanx. This may include freeing the base ofthe phalanx from the plantar plate if the health care provider cannotdistract the toe enough to place it on the distal head of the implant.Once properly exposed, the health care provider resects the head of theproximal phalanx and the base of the intermediate phalanx.

At a step 406, the health care provider creates pilot holes downintramedullary canals of both the proximal and intermediate phalanxusing the reamer 300. This may include observing laser marks to estimatedepth of the pilot hole so that the depth corresponds to the depthdetermined when selecting the implant based on size in step 402.Alternatively, a pre-drill with K-wire or a hand drill may be performedto form the pilot holes.

At a step 408, the health care provider broaches the pilot hole in eachphalanx with the broach 320. This increases the diameter of the pilothole to prepare it for receiving the device 100. Similar to step 408,this may include observing laser marks to estimate depth of the broachedhole so that the depth corresponds to the depth determined whenselecting the implant based on size in step 402. Broaching the hole mayconserve bone by compacting the cancellous bone of the phalanx to engagethe distal and proximal heads of the device 100 upon insertion. In someexamples, as indicated at step 410, the health care provider notes thebroach depth, and reevaluates, or evaluates for the first time, thelength of the device needed to achieve a desired fit in the broachedpilot hole.

Since the device 100 shown herein is a one-piece device formed ofsubstantially rigid material, it does not require special pre-operativehandling. For example, because it does not require deflection foranchoring as do some devices made of shape memory alloys, the device 100may be maintained at room temperature.

At a step 412, the health care provider grasps the device 100 using theinsertion forceps 340. This may include fitting the body 106 in therecesses 352, 354 of the insertion forceps 340 and securing the gripwith the locking mechanism 350. Further, it may include grasping thedevice 100 at a distance from an end that corresponds to the broachingdepth of the proximal phalanx. At a step 414, the health care provideraxially inserts the device 100 into the proximal phalanx, securing itinto the intramedullary canal. The insertion forceps may be used as apositive stop that prevents the implant from inadvertently beinginserted to a greater depth than desired. In addition, the surfaces onthe heads of the device 100 help the implant stay within the broachedcanal, while the taper helps reduce the likelihood of it catching oncancellous bone. Keeping the insertion forceps 340 attached to thedevice 100, the surgeon then grasps the digit of the toe with the distalportion of bone and places the digit over the distal aspect of thedevice 100 into the broached hole prepared in the intermediate phalanx,locking the device 100 into the intramedullary canal. This is thencompressed against the insertion tool 340. With both ends of the device100 in the respective, adjacent phalanges, the insertion forceps 340 maybe removed from the device 100.

At a step 416, the health care provider then grasps and compresses thetwo phalanges together to advance the proximal and distal ends of thedevice 100 deeper into both intramedullary canals to a final, lockedposition. Thus, the device 100 is completely intramedullary. At a step418, the wound is closed using the surgeon's preferred technique. Insome examples, either before or after closing the wound, the finalposition of the device 100 may be evaluated radiographically to ensurethat the phalanges are in close contact without gapping. Since thedevice 100 may be a single-use bone fixation device designed to bepermanently implanted in the medullary canal of the bone, follow-upprocedures and surgeries may be unnecessary. Although described withreference to the device 100, it would be apparent that the same methodwould be employed with any of the devices disclosed herein.

As indicated above, the exemplary device 100 may be used for treatmentsother than hammertoe, and in some examples, may be used to treatconditions in the fingers of a hand, or alternatively may be used totreat bone fractures. FIG. 11 is one example showing the device 100implanted within phalanges of the hand. The device 100 may be implantedin a manner substantially similar to that described above. In addition,removal of the device may be relatively easier than prior, conventionaldevices. For example, to remove the device, the cylindrical main bodymay be first cut, and then a cannulated drill may be fit over thecylindrical main body and drilled over to remove bony on-growth from thecylindrical body so that the arrowhead tip can be removed withouttearing the bone. This may prevent the health care provider from havingto cut the cortical bone in order to remove the implant. Accordingly,the cylindrical shape of the main body may help reduce a chance ofcompromising cortical bone during revision surgeries. Uses of the device100 may include but are not limited to hand surgery, orthopedic surgery,plastic surgery, and podiatric surgery. In addition, the implant may beinserted in a variety of angles that differ from its intended positionin medullary bone. In some examples, the implant may also be placedthrough cortical bone and tendon of the hand or foot.

In some examples, the device 100 is machined from a single piece of 316Lstainless steel, making it a weld-less, single monolith structure.Various lengths may be provided to meet patient sizing restrictions. Theoverall lengths of the device 100 may be in the range of 10 mm to 40 mm,while some lengths are within the range of 15 mm to 25 mm. When thedevice 10 is formed of a single piece of metal, potential stress-risersoccurring from welds or adhesives are eliminated and there is no need toassemble intra-operatively. Further, the material and size are selectedso that the device has bending and fatigue characteristics able toendure the forces exerted on the lesser toes.

In some examples, the arrowheads may be reconfigured at differentpositions to one another and may obtain the same stability to thearthrodesis/fracture site. For example, some embodiments have a proximalarrow vertical to the shaft or a distal arrow horizontal to the shaft.The same can be said for different angle increments to each arrow.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

I claim:
 1. An intramedullary fixation device used in bone fixation andstabilization, comprising: an arrowhead-shaped distal head comprising adistal end having a tip, the distal head having first, second, third,and fourth outwardly facing side surfaces forming a pyramidal shape, thefirst and third side surfaces being opposed from each other and forminga first angle, and the second and fourth side surfaces being opposedfrom each other and forming a second angle, the second angle beingdifferent than the first angle, each of the first and third sidesurfaces having a proximal edge configured to engage tissue and inhibitrotational movement and inhibit axial movement of the distal head in aproximal direction, the distal head being sized to fit within anintramedullary canal of a more-distal phalanx portion of one of a fingerand a toe; an arrowhead-shaped proximal head comprising a proximal endhaving a tip, the proximal head having fifth, sixth, seventh, and eighthoutwardly facing side surfaces, the fifth and seventh side surfacesbeing opposed from each other and forming a third angle, and the sixthand eighth side surfaces being opposed from each other and forming afourth angle, the third angle being different than the fourth angle,each of the fifth and seventh side surfaces having a distal edgeconfigured to engage tissue and inhibit rotational movement and inhibitaxial movement of the proximal head in a distal direction, the proximalhead being sized to fit within an intramedullary canal of amore-proximal phalanx portion of said one of a finger and a toe; and arigid body extending between and connecting the distal head and theproximal head, the body having a rigidity sufficient to withstandbending loading applied by the phalanges, the rigid body comprising amain portion, a distal neck portion connecting the rigid body to thedistal head, and a proximal neck portion connecting the rigid body tothe proximal head, the distal and proximal neck portions having across-sectional area smaller than a cross-section area of the mainportion such that tissue ingrowth may occur behind the distal headaround the distal neck portion and behind the proximal head around theproximal neck portion.
 2. The intramedullary fixation device of claim 1,wherein the side surfaces are smooth, planar surfaces.
 3. Theintramedullary fixation device of claim 1, wherein the first angle islarger than the second angle and the third angle is larger than thefourth angle.
 4. The intramedullary fixation device of claim 1, whereinthe first angle is larger than the third angle.
 5. The intramedullaryfixation device of claim 1, wherein the second and fourth side surfacesinclude proximal ends that relatively smoothly transition to the body.6. The intramedullary fixation device of claim 1, wherein the second andfourth surfaces intersect with a surface of the distal neck portion, andwherein the first and third surfaces do not intersect with a surface ofthe distal neck portion.
 7. The intramedullary fixation device of claim1, further comprising chamfered edges between adjacent outwardly facingside surfaces.
 8. The intramedullary fixation device of claim 1, whereinthe body comprises a first portion and a second portion, the firstportion being rigidly angled relative to the second portion at a fixedangle.
 9. The intramedullary fixation device of claim 8, wherein thefirst portion has a length less than a length of the second portion. 10.The intramedullary fixation device of claim 8, wherein the fixed angleis about a 10 degree angle.
 11. The intramedullary fixation device ofclaim 8, wherein the body is cylindrical and the first portion and thesecond portion have the same diameter.
 12. A kit for bone fixation andstabilization, comprising: an intramedullary fixation device,comprising: an arrowhead-shaped distal head comprising a distal endhaving a tip, the distal head having first, second, third, and fourthoutwardly facing side surfaces forming a pyramidal shape, the first andthird side surfaces being opposed from each other and forming a firstangle, and the second and fourth side surfaces being opposed from eachother and forming a second angle, the second angle being different thanthe first angle, each of the first and third side surfaces having aproximal edge configured to engage tissue and inhibit rotationalmovement and inhibit axial movement of the distal head in a proximaldirection, the distal head being sized to fit within an intramedullarycanal of a more-distal phalanx portion of one of a finger and a toe; anarrowhead-shaped proximal head comprising a proximal end having a tip,the proximal head having fifth, sixth, seventh, and eighth outwardlyfacing side surfaces, the fifth and seventh side surfaces being opposedfrom each other and forming a third angle, and the sixth and eighth sidesurfaces being opposed from each other and forming a fourth angle, thethird angle being different than the fourth angle, each of the fifth andseventh side surfaces having a distal edge configured to engage tissueand inhibit rotational movement and inhibit axial movement of theproximal head in a distal direction, the proximal head being sized tofit within an intramedullary canal of a more-proximal phalanx portion ofsaid one of a finger and a toe; and a rigid body extending between andconnecting the distal head and the proximal head, the body having arigidity sufficient to withstand bending loading applied by thephalanges, the rigid body comprising a main portion, a distal neckportion connecting the rigid body to the distal head, and a proximalneck portion connecting the rigid body to the proximal head, the distaland proximal neck portions having a cross-sectional area smaller than across-section area of the main portion such that tissue ingrowth mayoccur behind the distal head around the distal neck portion and behindthe proximal head around the proximal neck portion; and insertionforceps configured to securably grasp the intramedullary fixationdevice, the insertion forceps comprising: a first nose piece having afirst recess formed therein, the first recess being sized to receive aportion of the body of the intramedullary fixation device; a second nosepiece having a second recess formed therein, the second recess beingsized to receive a portion of the body of the intramedullary fixationdevice, the first and second nose pieces being cooperatively arranged tosecurely grip the body of the intramedullary fixation devicesufficiently to prevent rotation and axial displacement under normalinsertion conditions.
 13. The kit of claim 12, further comprising: areamer sized for insertion into an intramedullary canal of a human toe,the reamer having a first diameter; and a broach having a seconddiameter larger than the first diameter.
 14. An intramedullary fixationdevice used in bone fixation and stabilization, comprising: anarrowhead-shaped distal head comprising a distal end, the distal headhaving first, second, third, and fourth outwardly facing side surfacesforming a pyramidal shape, the first and third side surfaces beingopposed from each other and forming a first angle, and the second andfourth side surfaces being opposed from each other and forming a secondangle, the second angle being different than the first angle, the first,second, third, and fourth side surfaces converging toward the distalend, each of the first and third side surfaces having a proximallyprojecting edge configured to engage tissue and inhibit rotationalmovement and inhibit axial movement of the distal head in a proximaldirection, the distal head being sized to fit within an intramedullarycanal of a more-distal phalanx portion of one of a finger and a toe; anarrowhead-shaped proximal head comprising a proximal end, the proximalhead having fifth, sixth, seventh, and eighth outwardly facing sidesurfaces, the fifth and seventh side surfaces being opposed from eachother and forming a third angle, and the sixth and eighth side surfacesbeing opposed from each other and forming a fourth angle, the thirdangle being different than the fourth angle, the fifth, sixth, seventh,and eighth side surfaces converging and meeting at the proximal end,each of the fifth and seventh side surfaces having a distally projectingedge configured to engage tissue and inhibit rotational movement andinhibit axial movement of the proximal head in a distal direction, theproximal head being sized to fit within an intramedullary canal of amore-proximal phalanx portion of said one of a finger and a toe; and arigid body extending between and connecting the distal head and theproximal head, the body having a rigidity sufficient to withstandbending loading applied by the phalanges, the rigid body being sized andshaped to fit within the intramedullary canals of both the more-distalphalanx portion and the more-proximal phalanx portion, the distal head,proximal head, and rigid body being sized and shaped so that themore-distal phalanx portion may abut directly against the more-proximalphalanx portion when the distal head is in the more-distal phalanxportion and the proximal head is in the more-proximal phalanx portion.15. The intramedullary fixation device of claim 14, the rigid bodycomprising a main portion, a distal neck portion connecting the rigidbody to the distal head, and a proximal neck portion connecting therigid body to the proximal head, the distal and proximal neck portionshaving a cross-sectional area smaller than a cross-section area of themain portion such that tissue ingrowth may occur behind the distal headaround the distal neck portion and behind the proximal head around theproximal neck portion.
 16. The intramedullary fixation device of claim14, wherein the side surfaces are smooth, planar surfaces.
 17. Theintramedullary fixation device of claim 14, wherein the first angle islarger than the second angle and the third angle is larger than thefourth angle.
 18. The intramedullary fixation device of claim 14,wherein the first angle is larger than the third angle.
 19. Theintramedullary fixation device of claim 14, wherein the second andfourth side surfaces include proximal ends that relatively smoothlytransition to the body.
 20. The intramedullary fixation device of claim14, wherein the second and fourth surfaces intersect with a surface ofthe distal neck portion, and wherein the first and third surfaces do notintersect with a surface of the distal neck portion.